first things first i would get another opinion from a different shop have them actually show you the loose tie rods and the leaks i say that because i see a lot of cars coming in where shop a said i need all new tie rods and ball joints when its really only got bad ball joint or whatever if you have little experience and tools then the the rear main is probably not something you want to try as you have to remove the transmission if the rear diff is just a leaky cover then thats pretty easy if its a wheel seal or pinion seal itll be quite a bit more difficult but still potentially doable if youre willing to learn the tranny pan and valve cover gaskets are easy and shouldnt be a problem good luck